1. Field of the Invention
The present invention relates to a toner, and more specifically concerns an electrostatic-latent-image developing toner used for developing an electrostatic latent image in electrophotography, electrostatic recording, electrostatic printing and the like.
2. Description of the Related Art
Conventionally, an electrostatic-latent-image developing toner, which is used for developing an electrostatic latent image in electrophotography, electrostatic recording, electrostatic printing and the like, has been produced by a so-called pulverizing method in which a pigment such as carbon black is mixed in a thermoplastic resin and melt-kneaded into a uniformly dispersed matter, and then pulverized by an appropriate finely-pulverizing device into powder having a particle size required as a toner. However, the toner obtained by the above-mentioned melt-kneading/pulverizing method has a limitation in controlling the toner particle size, and it is difficult to produce a toner having an average particle size of virtually not more than 8 μm, in particular, not more than 6 μm with high yield. In recent years, there have been ever-increasing demands for small-size copying machines and for low power consumption and the resulting demands for toner capable of carrying out a fixing process at a temperature lower than that of the conventional toner. For this reason, a method in which a wax having a low softening point is blended into the toner at the time of kneading has been proposed; however, in the kneading/pulverizing method, the blending rate is limited to approximately 5%, failing to provide a toner having a sufficient low-temperature fixing property.
In order to achieve a sufficient low-temperature-fixing property, not only a fixing property at a lower temperature, but also a fixing separation property and an anti-offsetting property need to be maintained even at the time of fixing without using oil coat, while maintaining appropriate anti-breaking and anti-blocking properties at the time of storing toner or developing toner. Here, methods have been proposed in which: a boner having a core-shell structure is granulated through a suspension polymerization method, an emulsion polymerizing coagulation method, an emulsion dispersion method and the like that are capable of providing resin fine particles having a small particle size with a comparatively uniform particle size, and the toner particles are allowed to contain a wax (for example, U.S. Patent Application Publication US2002/0039699 and Japanese Patent Application Laid-Open No. 2002-229251).
At present, however, even a toner having a core-shell structure has not sufficiently satisfied all the properties such as a property of low-fixing temperature, an anti-offsetting property, an anti-breaking property and an anti-blocking property.